We are saddened to share disappointing news from Acadia Pharmaceuticals. The Phase 3 COMPASS clinical trial evaluating intranasal carbetocin (ACP-101) in individuals with PWS did not meet its primary endpoint of reducing hyperphagia. The study also showed no meaningful difference from placebo on secondary measures.
“Acadia approached this trial with great care and respect for our community,” said Theresa Strong, Director of Research Programs at FPWR. “Their willingness to listen to families and incorporate patient perspectives into the study design reflects the kind of partnership that moves the entire field forward, even when results fall short of our hopes.”
“For families who saw benefit, this news is devastating,” added Susan Hedstrom, FPWR’s Executive Director. “We know how much hope is carried into every trial, and how heavy the weight feels when those hopes are not realized.”
While the trial did not achieve the outcome we had hoped for, we remain grateful to the families who participated in this study and to Acadia for partnering with our community in our search for effective treatments.
We continue to hold hope for new treatments and remain committed to advancing research until every person with PWS can lead the full and independent life they deserve.
Acadia's full press release:
SAN DIEGO—(BUSINESS WIRE)—Sep. 24, 2025—Acadia Pharmaceuticals Inc.(Nasdaq: ACAD) today announced top-line results from the Phase 3 COMPASS PWS trial evaluating the efficacy and safety of intranasal carbetocin (ACP-101) in patients with hyperphagia in Prader-Willi syndrome (PWS). Intranasal carbetocin did not demonstrate a statistically significant improvement over placebo on the study’s primary endpoint, change from baseline to Week 12 on the Hyperphagia Questionnaire for Clinical Trials (HQ-CT), nor was there separation from placebo on any secondary endpoint. The safety and tolerability profile of intranasal carbetocin was consistent with previous clinical trials, showing a low rate of adverse events.
“We are disappointed by these findings, especially for Prader-Willi syndrome patients, their families and the entire community,” said Elizabeth H.Z. Thompson, Ph.D., Acadia’s Head of Research and Development. “I want to thank the many patients, families, study site personnel, and physicians who participated in the COMPASS PWS study as well as the intranasal carbetocin clinical development program, for their dedication and contributions in this important study. We are committed to sharing a summary of the data in the future to ensure learning for the PWS community; however, given these results, we do not intend to investigate intranasal carbetocin any further.”
COMPASS PWS was a 12-week, double-blind, randomized, placebo-controlled global Phase 3 trial evaluating the efficacy and safety of intranasal carbetocin 3.2 mg three times daily (TID) in 175 enrolled children and adults aged five to 30 years with PWS.
“Despite this disappointment, Acadia is well-positioned to deliver long-term, sustainable growth supported by two approved products projected to generate over $1 billion in net sales in 2025, and a robust pipeline that includes eight disclosed and multiple undisclosed programs,” said Catherine Owen Adams, Acadia’s Chief Executive Officer. “Looking ahead, we anticipate seven Phase 2 or 3 study starts through 2026 and four data readouts by the end of 2027. For more details on our programs, I encourage you to revisit our recent R&D Day presentation on our website.”
